Recording apparatus for magnetic disks using both sides of the disk

ABSTRACT

Magnetic disk recording apparatus including a pair of magnetic transducers contacting the opposite sides of a magnetic disk and each carried by a swingable arm. The arms are interconnected together so that the swinging movement of one of the arms is transmitted to the other arm to cause an opposite swinging movement of the other arm for simultaneously moving the transducers away from the magnetic disk. An electro-magnet actuates one of the arms so as to thereby also move the other arm.

.Iadd.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to Daniel O. Castrodale et al. applicationfor Data Storage Apparatus Using A Flexible Magnetic Disc, Ser. No.570,118, filed Apr. 21, 1975 and to a continuation of said applicationby Daniel O. Castrodale et al., Ser. No. 776,456, filed Mar. 10, 1977for Data Storage Apparatus Using A Flexible Magnetic Disk. .Iaddend.

BACKGROUND OF THE INVENTION

The invention relates to magnetic recording apparatus and particularlyto apparatus for recording on magnetic disks.

It has previously been common practice to record only on one side of aflexible magnetic disk at a time. Such recording, of course, limits thecapacity of the apparatus with respect to the total amount ofinformation that may be recorded and the speed with which theinformation may be recorded.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide improved recordingapparatus by means of which two-sided recording may be accomplished on amoving magnetic medium and particularly on a flexible magnetic disk forthereby providing increased capacity and speed of recording. In thisconnection, it is an object of the invention to provide a pair ofmagnetic transducers effective on the opposite sides of a magnetic diskand means for holding the transducers in simultaneous contact with thedisk so that simultaneous data transfer may take place on the two sidesof the disk.Iadd., assuming that the proper electrical connections foreither a reading or a writing action are completed to both of thetransducers at the same time.Iaddend..

It is a further object of the invention to provide improved means forcarrying such a pair of transducers so that the two transducers aremoved simultaneously into recording engagement with the opposite sidesof a magnetic disk and are moved simultaneously out of contact with thedisk when it is desired to remove the disk from between the transducers.

More specifically, it is an object of the invention to provide a pair ofarms on which the two transducers are mounted and to interconnect thearms so that the movement of one arm automatically causes the other armto move, so that the two transducers are simultaneously moved withrespect to the disk. In this connection, it is an object of theinvention to provide power mechanism operative on one of the arms tothereby simultaneously move both of the arms and their magnetictransducers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view, partially schematic, of magnetic diskrecording apparatus including a pair of magnetic transducers positionedon opposite sides of a magnetic disk by means of a pair of swing armscarrying the transducers;

FIG. 2 is a sectional view taken on line 2--2 of FIG. 1;

FIG. 3 is a sectional view on an enlarged scale taken on line 3--3 ofFIG. 2;

FIG. 4 is a view similar to FIG. 1 of another form of the invention;

FIG. 5 is a view similar to FIGS. 1 and 4 of still another form of theinvention including a pair of transducer carrying swing arms that areconnected by means of a flexure integrally molded with the swing arms;and

FIG. 6 is a fragmentary view in side elevation of the two swing arms ofthe FIG. 5 form of the invention, with the swing arms being in differentpositions than those shown in FIG. 5 and being swung outwardly todisengage the magnetic transducers carried thereby with respect to theassociated magnetic disk.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 in particular, the magnetic head load mechanismshown therein may be seen to comprise a pair of arms 10 and 12 onopposite sides of a magnetic disk 14. The magnetic disk 14 at its centeris fixed on a rotatable drive shaft 16 and may be of a thin flexiblematerial, such as polyethylene terephthalate of about 0.003 inchthickness, for example. The disk 14 is coated on both sides with amagnetic material, such as iron oxide.

The arms 10 and 12 are respectively mounted on a carriage 18 by means ofcantilever leaf springs 20 and 22. The carriage 18 is slideably disposedon fixed guide rods 23 extending through the carriage 18. The springs 20and 22 may have their upper ends embedded in the arms 10 and 12, and thelower ends of the springs 20 and 22 may be fixed with respect to thecarriage 18 by means of screws 24. A pair of loading leaf springs 26 and28 are fixed with respect to the carriage 18 by means of the screws 24and bear respectively on rounded protrusions 30 and 32 on the arms 10and 12. The arm 10 is provided with a slider portion 34 which underliesa slider portion 36 of the arm 12 whereby the portion 34 may cause aswinging movement of the portion 36 and thereby of the arm 12 as will bedescribed in greater detail hereinafter.

The springs 26 and 28 urge the arms 10 and 12 toward each other, and thecarriage 18 carries a pair of stops 38 and 40 for limiting the motion ofthe arms 10 and 12 toward each other. The arms 10 and 12 respectivelycarry magnetic transducers 42 and 44 of similar construction. Thetransducer 42 is shown in section in FIG. 3, and it will be observedthat the transducer 42 is hollow and fits over a head guide 46 integralwith the arm 10. A spring 48 is disposed between the head guide 46 andan opposite internal surface of the transducer 42 and urges a magnetichead 50 on the end of the transducer 42 into forceful engagement withthe disk 14. A plurality of headed studs 52 extend through the arm 10and into the transducer 42 for the purpose of limiting the movement ofthe transducer 42 under the action of the spring 48 under the conditionsin which the transducer 42 is separated from the disk 14 as will bedescribed.

The carriage 18 is carried by and is fixed with respect to a flexiblebelt 54 that extends around spaced pulleys 56 and 58. The pulley 56 isrotatably mounted on an axle 60 having a spring 62 effective on theaxle. The pulley 58 is fixed on the output shaft 64 of a motor 66 whichis preferably of the electrical stepping type. The belt 54 is fixed byany suitable means with respect to the pulley 58.

An electric solenoid 68 (see FIG. 2) is mounted on a stationary part 70and is effective on an armature portion 72 of a lever 74. The lever 74pivots about an edge 70a of the stationary part 70. A spring 76 iseffective between the lever 74 and the stationary part 70, and the part70 has an abutment edge 70b which limits the pivoting movement of thelever 74 about the edge 70a under the action of the spring 76. The arm10 carries a hook 78 that encompasses the lever end 74a. The lever end74a has an increased width with respect to the rest of the lever 74 tofunction as a lost motion connection between lever 74 and arm 10 andallow for a substantial movement of the carriage 18 along the stationaryguide rods 23.

In operation, the transducers 42 and 44 are normally held in contactwith opposite sides of the flexible disk 14 as shown in FIGS. 1 and 2,and the disk 14 is rotated by means of its drive shaft 16 on which thedisk 14 is mounted. The arms 10 and 12 are held against the stops 38 and40 by means of the springs 26 and 28, and the springs 48 maintain thetransducers 42 and 44 in engagement with the disk 14 under a pressure asdetermined by the springs 48. The transducers 42 and 44 may thus be usedfor reading and writing magnetically on the surfaces of the disk 14 bymeans of the magnetic heads 50 in the transducers 42 and 44 whichdescribe circular tracks or paths on the opposite sides of the disk 14as it rotates. The carriage 18 is moved along the guide rods 23 by meansof the motor 66, so that the transducers 42 and 44 move to differentconcentric tracks on the surfaces of the disk 14. The motor 66 drivesthe belt 54 about the pulleys 56 and 58; and, since the carriage 18 isfixed with respect to the belt 54, the carriage 18 and the transducers42 and 44 likewise move, this movement being in a direction toward oraway from the center of the drive shaft 16 for the disk 14.

When it is desired to disengage the transducers 42 and 44 from the disk14, such as for the purpose of releasing the disk 14 for replacement byanother similar disk having different information on it, theelectromagnet 68 is de-energized. The lever .[.78.]. .Iadd.74.Iaddend.is thus swung about the pivot edge 70a by the action of thespring 76, and the lever 74 in this swinging movement likewise moves thearm 10 against the action of the spring 26. The spring 20 acts as aflexure joint and allows this movement of the arm 10, which iscounterclockwise as seen in FIG. 1 about the spring 20 acting as ajoint. The slider portion 34 of the arm 10 underlies the slider portion36 of the arm 12, and the slider portion 34 in pivoting with the rest ofthe arm 10 acts on the slider portion 36 of the arm 12 and causes asimilar pivoting action of the arm 12. The arm 12 pivots about thespring 22, which functions also as a flexure joint similarly to thespring 20 for the arm 10; and the arm 12 pivots in a clockwise directionas seen in FIG. 1 about the spring 22 acting as a flexure joint. Thetransducers 42 and 44 move along with the arms 10 and 12 and thusrespectively pivot in the counterclockwise and clockwise directions toseparate from the disk 14. The disk 14 may then be replaced as desired.The electromagnet 68 is energized to swing the lever 74 about the pivotedge 70a back into its FIG. 2 position in order to allow the spring 26and 28 to return the arms 10 and 12 and the transducers 42 and 44 backinto their positions of FIGS. 1 and 2 in which the transducers 42 and 44engage the disk 14.

The form of the invention illustrated in FIG. 4 is basically the same asthat illustrated in the preceding figures, but the arms 10a and 12acorresponding to the arms 10 and 12 are pivotally mounted on thecarriage 18a corresponding to the carriage 18 instead of being mountedby means of cantilever leaf springs. More specifically, the arms 10a and12a are pivotally mounted on the carriage 18a by means of pivot shafts80 and 82. Torsion springs 84 and 86 extend around the shafts 80 and 82and bear against the arms 10a and 12a for the purpose of forcing thearms 10a and 12a together. The torsion springs 84 and 86 are used inlieu of the leaf springs 26 and 28 in the first embodiment.

The embodiment shown in FIGS. 5 and 6 is basically the same as thatshown in FIGS. 1-3, the principal difference between the FIGS. 5 and 6embodiment and the first described embodiment being that a thin sectionflexure 90 is substituted for the slider portions 34 and 36. The arms10b and 12b corresponding to the arms 10 and 12 in the first describedembodiment are molded along with the flexure 90 in one piece, being of aplastic which at least in thin sections is quite flexible. It will benoted that the flexure 90 as seen in FIG. 5 simply constitutes arelatively thin upwardly bowed portion which is integral with the arms10b and 12b and connects with these arms at points 90a and 90b. Thecarriage 18b which is slideably mounted on the guide rods 23 and whichcorresponds with the carriage 18 in the first described embodiment has apair of upstanding rails 92 and 94 molded on it, and the arms 10b and12b have grooves 96 and 97 molded into them which fit on the rails 92and 94. The rails 92 and 94 and the grooves 96 and 97 are semicircularin cross sectional shape so that the arms 10b and 12b may easily swingon the rails 92 and 94. The centers of these rails and grooves aresubstantially equidistant from the attachment points 90a and 90b. Thearms 10b and 12b may together be slid onto the rails 92 and 94 inassembling the FIG. 5 form of the invention, and the arms 10b and 12bmay be held by any suitable means, such as "C" clips (not shown), fromsliding off of the rails 92 and 94. A pair of leaf springs 98 and 100are fixed with respect to the carriage 18b and bear on the arms 10b and12b for the purpose of holding the arms 10b and 12b against the stops 38and 40 so that the transducers 42 and 44 bear with pressure on the disk14.

The embodiment of FIGS. 5 and 6 operates basically the same as the firstdescribed embodiment. The springs 98 and 100 hold the transducers 42 and44 against the surfaces of the disk 14 for a magnetic reading or writingaction. When the electromagnet 68 is de-energized, the lever 74 pullsthe arm 10b so as to rotate the arm 10b in the counterclockwisedirection as seen in FIG. 5 about the rail 92, moving the transducer 42away from the disk 14. The flexure 90 transmits a force in the upwarddirection as the parts are shown in FIGS. 5 and 6 from the arm 10b tothe arm 12b, causing the arm 12b to rotate in the clockwise directionand moving the transducer 44 away from the disk 14 at the same time asthe transducer 42 is moved away from the disk 14. The arms 10b and 12bare shown fragmentarily in FIG. 6 in their positions in which thetransducers 42 and 44 are separated from the disk 14, and it will beobserved that under these conditions the flexure 90 not only transmitsan upward force to the arm 12b at the attachment point 90b, but theflexure 90 has also elongated in order to compensate for the increaseddimension A measured between the attachment points 90a and 90b.

The various forms of the invention above described provide two-sidedrecording on the magnetic disk 14 for increased capacity. They load bothof the transducers 42 and 44 on the disk 14 at the same time so thatboth of the transducers 42 and 44 may be simultaneously effective forreading or writing magnetically on the disk 14.Iadd., assuming that theelectrical connections to both of the transducers 42 and 44 arecompleted at the same time for either a reading action or a writingaction.Iaddend.. In all forms of the invention, the two arms, the arms10 and 12 in the first described form and the corresponding arms in theother forms of the invention, move simultaneously due to the connectionfrom one arm to the other arm; and, therefore, only the singleelectromagnet 68 is necessary in order to cause movement of the two armsin each form of the invention. All forms of the invention are relativelysimple and may be manufactured at relatively low cost. No particularpivots are needed for the arms 10 and 12 in the first describedembodiment, since the cantilever leaf spring flexures 20 and 22 provideall of the pivoting action needed. The form of the invention illustratedin FIGS. 5 and 6 is considered particularly economical of manufacture,since the arms 10b and 12b along with the flexure 90 are integralparts--only one molding operation is thus necessary for producing thethree parts 10b, 12b and 90.

We claim:
 1. Magnetic recording apparatus comprising a magnetic mediumhaving opposite sides both of which have a magnetic surface, a pair oftransducers for magnetic action on the opposite sides of said medium,means for moving said magnetic medium so that a track or path isdescribed by each of said transducers on a side of said medium, firstand second swing arms each carrying one of said transducers, a carriage,a swing mounting for said first arm with respect to said carriage, aswing mounting for said second arm with respect to said carriage, meansfor moving said carriage and thereby said arms and said transducers in adirection at angles to said track so that the transducers traverse themagnetic medium on other tracks of the magnetic medium, an arm portionfixed with respect to said second swing arm adjacent to its swingmounting with said carriage and extending toward said first swing arm,and an arm portion fixed with respect to said first swing arm adjacentto its swing mounting with said carriage and extending toward saidsecond swing arm to form a power transmitting connection with said armportion of said second swing arm so as to swing said second swing armand said transducer carried thereby away from said medium when saidfirst swing arm is swung about its swing mounting with said carriage tomove said first swing arm and said transducer carried thereby away fromsaid medium.
 2. Magnetic recording apparatus as set forth in claim 1,said medium being a magnetic disk and said means for moving said mediumconstituting a shaft extending through the center of the disk on whichthe disk is mounted.
 3. Magnetic recording apparatus as set forth inclaim 2 and including power means for swinging said first swing arm in adirection away from said medium to separate said transducer carriedthereby from said medium and thereby moving said second swing arm awayfrom said medium to separate said transducer carried by said secondswing arm from said medium, and spring means for restoring said swingarms to initial positions in which said transducers are in datatransferring relationship with respect to said medium.
 4. Magneticrecording apparatus as set forth in claim 3, said power means includinga motor and a lever swung under the action of said motor, and a hookcarried by said first swing arm and extending around said lever to as toprovide a lost motion connection with said lever so that the leverretains its connection with said first swing arm as said carriage movesto move said transducers from said first named track to other tracks onsaid disk.
 5. Magnetic recording apparatus as set forth in claim 1, saidarm portion fixed with respect to said first swing arm underlying saidarm portion fixed with respect to said second swing arm so that as saidfirst swing arm is swung about its swing mounting with said carriage tomove its said transducer away from said medium said arm portion on saidfirst swing arm bears against said arm portion of said second swing armand rotates said second swing arm concommitantly with said first swingarm.
 6. Magnetic recording apparatus as set forth in claim 1, said swingmounting for each of said swing arms including a leaf flexure springconnecting each of said swing arms with said carriage.
 7. Magneticrecording apparatus comprising a magnetic medium having opposite sidesboth of which have a magnetic surface, a pair of transducers formagnetic action on the opposite sides of said medium, means for movingsaid magnetic medium so that a track or path is described by each ofsaid transducers on a side of said medium, a pair of swing arms eachcarrying one of said transducers, a carriage, means for swingablymounting said arms on said carriage, means for moving said carriage andthereby said arms and said transducers in a direction at angles to saidtrack so that the transducers traverse the magnetic medium on othertracks of the magnetic medium, means interconnecting a first one of saidarms with a second one of said arms so that when said first arm is swungto move said transducer carried thereby away from said medium the otherarm is thereby swung also to move its transducer away from said medium,said medium being a magnetic disk and said means for moving said mediumconstituting a shaft extending through the center of the disk on whichthe disk is mounted, said means for swingingly mounting said arms onsaid carriage including a leaf flexure spring for each of said arms andhaving one end embedded in the arm and having its opposite end fixed tosaid carriage at a point of attachment, and a leaf return spring foreach of said arms fixed to said carriage at a said point of attachmentand extending to an exterior surface of the arm whereby to return thearm to a position in which its said transducer is in data transferringposition with respect to said disk.
 8. Magnetic recording apparatuscomprising a magnetic medium having opposite sides both of which have amagnetic surface, a pair of transducers for magnetic action on theopposite sides of said medium, means for moving said magnetic medium sothat a track or path is described by each of said transducers on a sideof said medium, a pair of swing arms each carrying one of saidtransducers, a carriage, means for swingingly mounting said arms on saidcarriage, means for moving said carriage, and thereby said arms and saidtransducers in a direction at angles to said track so that thetransducers traverse the magnetic medium on the other tracks of themagnetic medium, means interconnecting a first one of said arms with asecond one of said arms so that when said first arm is swung to movesaid transducer carried thereby away from said medium the other arm isthereby swung also to move its transducer away from said medium, saidmedium being a magnetic disk and said means for moving said mediumconstituting a shaft extending through the center of the disk on whichthe disk is mounted, said means for swingingly mounting said arms onsaid carriage including a pivot shaft extending through each of saidarms about which the arm may pivot, and springs extending around saidshafts and in contact with the associated swing arm .[.in.]. .Iadd.and.Iaddend.with said carriage for yieldably moving said swing arms towardeach other so as to bring said transducers into data transferringrelationship with respect to said disk.
 9. Magnetic recording apparatuscomprising a magnetic medium having opposite sides both of which have amagnetic surface, a pair of transducers for magnetic action on theopposite sides of said medium, means for moving said magnetic medium sothat a track or path is described by each of said transducers on a sideof said medium, a pair of swing arms each carrying one of saidtransducers, a carriage, means for swingingly mounting said arms on saidcarriage, means for moving said carriage and thereby said arms and saidtransducers in a direction at angles to said track so that thetransducers traverse the magnetic medium on other tracks of the magneticmedium, and means interconnecting a first one of said arms with a secondone of said arms so that when said first arm is swung to move saidtransducer carried thereby away from said medium the other arm isthereby swung also to move its transducer away from said medium, saidmedium being a magnetic disk and said means for moving said mediumconstituting a shaft extending through the center of the disk on whichthe disk is mounted, said means interconnecting said arms including arelatively thin flexure section which extends between and is integralwith said arms, said flexure section being of relatively flexiblematerial so that when said first arm is swung to move its transduceraway from said disk the other of said arms is swung likewise to move itstransducer away from said disk with bending of said flexure section. 10.Magnetic recording apparatus as set forth in claim 9, said means forswingingly mounting said arms on said carriage including for each ofsaid arms a rail with a rounded periphery carried by said carriage andfitting within a rounded cavity in the arm, said relatively thin flexuresection having points of attachment to each of said arms which arelocated at substantially the same distances away from the respectiverails and said flexure section being curved outwardly from said railswhen said arms are in positions in which said transducers are closelyadjacent to the surfaces of said disk for data transferring action. 11.Magnetic recording apparatus as set forth in claim 10 and including apair of leaf springs attached to said carriage and extending therefromto outer surfaces of said arms for returning said arms to positions inwhich said transducers are closely adjacent to the surfaces of said diskfor data transferring action. .Iadd.
 12. A magnetic transducer carriageassembly for use with a moving magnetic medium, comprising:a carriageadapted to be moved transversely of a moving magnetic medium, a pair oftransducers for magnetic action on the opposite sides of the medium,first and second swing arms each carrying one of said transducers, aswing mounting for said first arm with respect to said carriage, a swingmounting for said second arm with respect to said carriage, an armportion fixed with respect to said second swing arm adjacent to itsswing mounting with said carriage and extending toward said first swingarm, and an arm portion fixed with respect to said first swing armadjacent to its swing mounting with said carriage and extending towardsaid second swing arm to form a power transmitting connection with saidarm portion of said second swing arm so as to swing said transducercarried by said second swing arm away from said transducer carried bysaid first swing arm and thereby away from a magnetic medium positionedbetween said transducers when said first swing arm is swung about itsswing mounting with said carriage to move said transducer carriedthereby away from said other transducer and thereby away from a magneticmedium positioned between said transducers. .Iaddend. .Iadd.
 13. Amagnetic transducer carriage assembly as set forth in claim 12 andincluding spring means for restoring said swing arms to initialpositions in which said transducers are in close proximity and may be indata transferring relationship with respect to a magnetic medium betweensaid transducers. .Iaddend..Iadd.
 14. A magnetic transducer carriageassembly as set forth in claim 12; said arm portion fixed with respectto said first swing arm underlying said arm portion fixed with respectto said second swing arm so that, as said first swing arm is swung aboutits swing mounting with said carriage to move its said transducer awayfrom said other transducer and thereby away from a magnetic mediumbetween said transducers, said arm portion on said first swing arm bearsagainst said arm portion of said second swing arm and swings said secondswing arm concomitantly with said first swing arm. .Iaddend..Iadd.
 15. Amagnetic transducer carriage assembly as set forth in claim 12, saidswing mounting for each of said swing arms including a leaf flexurespring connecting the swing arm with said carriage. .Iaddend..Iadd. 16.A magnetic transducer carriage assembly as set forth in claim 15, saidleaf flexure spring for each of said arms having one end embedded in thearm and having its opposite end fixed to said carriage at a point ofattachment, and a leaf return spring for each of said arms fixed to saidcarriage at said point of attachment for this arm and extending to anexterior surface of the arm whereby to return the arms to positions inwhich their said transducers are in close proximity and are in datatransferring position with respect to a magnetic medium between saidarms. .Iaddend..Iadd.
 17. A magnetic transducer carriage assembly as setforth in claim 12; said power transmitting connection between said armportions including a relatively thin flexure section which extendsbetween and is integral with said arm portions; said flexure sectionbeing of relatively flexible material so that, when said first arm isswung, it causes the other of said arms to swing likewise but in anopposite direction so as to separate said transducers with bending ofsaid flexure section. .Iaddend..Iadd.
 18. Magnetic recording apparatusfor utilizing a magnetic disk both sides of which have a magneticsurface, said apparatus comprising:a pair of transducers for magneticaction on the opposite sides of the disk, rotary driving means fordrivingly rotating the disk about its center, first and second swingarms each carrying one of said transducers, a carriage, a swing mountingfor said first arm with respect to said carriage, a swing mounting forsaid second arm with respect to said carriage, means for moving saidcarriage and thereby said arms and said transducers in a directiongenerally toward said driving means so that the transducers traverseacross concentric tracks on the disk, an arm portion fixed with respectto said second swing arm adjacent to its swing mounting with saidcarriage and extending toward said first swing arm, and an arm portionfixed with respect to said first swing arm adjacent to its swingmounting with said carriage and extending toward said second swing armto form a power transmitting connection with said arm portion of saidsecond swing arm so as to swing said second swing arm and thereby moveits said transducer away from said transducer carried by said firstswing arm and from a disk disposed between said transducers when saidfirst swing arm is swung about its swing mounting with said carriage tomove its said transducer in a direction away from said other transducer..Iaddend..Iadd.
 9. Magnetic recording apparatus as set forth in claim 18and including:power means for swinging said first swing arm in adirection to move its said transducer away from said other transducer toseparate said transducers, and spring means for restoring said springarms to initial positions in which said transducers are in closeproximity for a data transferring relationship with respect to a disktherebetween. .Iaddend. .Iadd.
 20. Magnetic recording apparatus as setforth in claim 18, said arm portion fixed with respect to said firstswing arm underlying said arm portion fixed with respect to said secondswing arm so that, as said first swing arm is swung about its swingmounting with said carriage to move its said transducer away from saidother transducer, said arm portion on said first swing arm bears againstsaid arm portion of said second swing arm and swings said second swingarm concomitantly with said first swing arm to separate saidtransducers. .Iaddend..Iadd.
 21. Magnetic recording apparatus as setforth in claim 18, said swing mounting for each of said swing armsincluding a leaf flexure spring connecting the swing arm with saidcarriage. .Iaddend..Iadd.
 22. Magnetic recording apparatus as set forthin claim 18; said power transmitting connection between said armportions including a thin flexure section which extends between and isintegral with said arm portions, said flexure section being ofrelatively flexible material so that, when said first arm is swung in adirection to move its said transducer away from said other transducer,said second arm is swung oppositely so as to move said transducers apartwith bending of said flexure section. .Iaddend.